Bimetallic circuit overload protector

ABSTRACT

A thermal overload protector for electrical circuits usable in single and multiphase circuits. A bimetallic element actuates a snap action switch in response to excess current in a heater connected in the circuit. An adjusting cam engages a switch element to permit adjustment of the operating value over a range while a reset cam can be actuated to provide for manual or automatic reset. Part of the switch operating linkage can be formed from a bimetal to provide an ambient compensating element. Also included are screws acting on the actuating linkage to permit precise adjustment during manufacture to compensate for such manufacturing tolerances as may exist. The protector may be constructed in either a normally closed or a transfer contact configuration.

United States Patent 1 Sitar BIMETALLIC CIRCUIT OVERLOAD PROTECTOR [4 1 Mar. 27, 1973 Primary Examiner-l-larold Broome Att0meyMcDougall, Hersh & Scott [57] ABSTRACT A thermal overload protector for electrical circuits usable in single and multiphase circuits. A bimetallic element actuates a snap action switch in response to excess current in a heater connected in the circuit. An adjusting cam engages a switch element to permit adjustment of the operating value over a range while a reset cam can be actuated to provide for manual or automatic reset. Part of the switch operating linkage can be formed from a bimetal to provide an ambient compensating element. Also included are screws acting on the actuating linkage to permit precise adjustment during manufacture to compensate for such manufacturing tolerances as may exist. The protector may be constructed in either a normally closed or a transfer contact configuration.

25 Claims, 15 Drawing Figures PATENTEBMARZ? ms 3, 723, 929

SHEET 3 [IF 4 FIG. 12

PATENTEDMARZY 1975 FIG, 14

SHEET [1F 4 BIMETALLIC CIRCUIT OVERLOAD PROTECTOR BACKGROUND OF THE INVENTION This invention relates generally to electrical circuit controlling means. More specifically, it relates to devices for protecting electrical loads from possible damage due to excessive current flowing in an electrical circuit.

Electrical circuit protective means designed to protect electrical loads against excessive current by utilizing elements which are temperature responsive and ble in a single device where heretofore such has not been the case.

Therefore, it is an object of this invention to provide a novel electrical circuit protection device which includes in a single device a number of different capabilities and features.

It is another object of this invention to provide a 7 novel electrical circuit protection device which is capable of providing thermal or current protection in a single or a multiphase circuit as required by a user.

It is still another object of this invention to provide a novel electrical circuit protection device which may be adjusted by the user to adjust the nominal operating value of a given device.

It is a further object of this invention to provide a I novel electrical circuit protection device which is capable of functioning at its rated operating parameter substantially independent of variations in the ambient temperature of its environment.

It is a still further object of this invention to provide a novel electrical circuit protection device which can be arranged to automatically restore the circuit or alternatively to require an operator to manually do the same.

It is another object of this invention to provide a novel electrical circuit protection device which may include means for providing an indication that the device has operated.

A further object of this invention is to provide a novel electrical circuit protection device in which various means for determining its mode of operation and its operating value are convenient and relatively accessible. i

A still further object of this invention is to provide a novel electrical circuit protection device which in- .cludes a means whereby it may be tested as desired by a user to insure that it is capable of functioning as needed.

Another object of this inventionis to provide a novel circuit protection device which includes adjustments means which may be used during manufacture to provide for arelatively accurate determination of rated operating values independent of variations in the tolerances of the materials used.

BRIEF SUMMARY OF THE INVENTION The foregoing and other objects are achieved in an embodiment of the invention wherein bimetallic actuators are arranged to be exposed to heaters connected in an electrical circuit to be protected so as to respond to the heat created in such heaters by current flowing in the circuit and upon the movement of any one or more of the actuators to cause a switch means to operate to thereby provide an electrical signal effective to actuate a circuit interrupting device so as to prevent further current flow in the circuit and thereby protect the same. If desired, means may be provided to render the device substantially independent of variations in the ambient temperature of the environment in which it is used. Likewise, means may be provided to permit an automatic reclosure or to require a manual reclosure as desired.

BRIEF DESCRIPTION OF THE DRAWINGS The invention itself is set forth in the claims appended hereto and forming a part of the specification while an understanding of its structure and mode of operation may be derived from the detailed description taken in conjunction with the drawings in which:

FIG. 1 is a plan view partially in section of a circuit protective device in accordance with the invention;

FIG. 2 is a side view of the device of FIG. 1;

FIG. 3 is a bottom view of the device of FIG. 1;

FIG. 4 is a sectional view along the line 4-4 of FIG.

FIG. 5 is an exploded side view of the device in FIG. I;

FIG. 6 is a view along the line 66 of FIG. 5;

FIG. 7 is a view along the line 77 of FIG. 5;

FIG. 8 is a view along the line 88 of FIG. 5;

FIG. 9 is a view along the line 99 of FIG. 5;

FIG. 10 is a view along the line l010 of FIG. 4;

FIG. 11 is a view along the line 11-1 1 of FIG. 4;

FIG. 12 is a view along the line l2l2 of FIG. 1;

. FIG. 13 is a view along the line l313 of FIG. 12',

FIG. 14 is an exploded view of the movable contact forming a part of the invention; and

FIG. 15 is an exploded view of the basic elements of tIOlI.

DETAILED DESCRIPTION As may best be seen in FIGS. 1, 2, 3 and 5, there is provided a housing designated generally by the reference numeral 2. The housing is constituted by an upper body 4 and a lower body 6. The body is completed by a back plate 8 secured to the lower body 6 by a plurality of screws 10 as is best shown in FIG. 3. The housing 2 is formed of any suitable plastic or similar insulating material and includes a plurality of ledges or supporting surfaces, openings and dividers for maintaining the various operating elements in their desired assembled position.

Supported on the upper body 4 are .a plurality of terminals 12 and 14. Each terminal l2 is physically separated from an adjoining terminal 12 and each terminal I4 is physically separated from an adjoining terminal 14 by dividers 16 molded integrally with the upper body 4 for the purpose of assuring good electrical separation therebetween. The various terminals are attached to the housing by means of screws 18 passing through the lower body 6, the upper body 4 and engaging in threaded openings provided in the terminals. The screws 18 are provided with heads which are accessible from the bottom of the housing by means of recesses 20 v molded in the lower body 6 and in addition to retaining the terminals on the housing also function to hold the lower body 6 assembled to the upper body 4.

Each terminal 12 and 14 includes headed screws 22 for connecting the terminals to heating elements 24 (only two of which are shown) extending between the terminals 14 and 12. As may be seen, the device as disclosed includes three sets of terminals 12 and 14 whereby the device may be used to provide circuit protection in a three-phase circuit. If desired, only one set of terminals may be utilized if the circuit to be protected is a single-phase circuit.

Mounted within the upper body 4 are bimetallic elements 26. The bimetallic elements 26, as may be best seen in FIGS. 4 and 11, are mounted in the upper body by screws 28 anchoring one of their ends to a ledge or shoulder molded in the upper body and are positioned so that their lengths extend tothe opposite side of the housing and are disposed beneath the heating elements 24 with their opposite ends 29 therefore free to move downwardly in response to heat generated in the heating elements caused by current flow therein. Means for adjusting each bimetal 26 (See FIG. 4) are provided in the form of a screw 31 threaded into the upper body 4. v A ball 33 rests on the upper end of the screw and bears As may best be seen in FIGS. 4 and 10, the movable ends 29 of the bimetallic elements 26 are in physical contact with the spaced extensions 30 of a coupler 32. The coupler 32 is formed from an electrically insulating material such as a phenolic resin and consists of the upper extensions 30, a cross bar 34 and lower extensions 36. As shown in FIG. 10, the two outer upper extensions 30 are formed with upwardly extending portions 38 engaging the outer sides of the two outer bimetallic elements 26 so as to be held against transverse movement with respect to those elements. Also,

- as shown in FIG. 10, the lower extensions 36 of the coupler 32 are provided with downwardly depending projections 40 for .a similar purpose, as will be described.

At its bottom the coupler 32 engages a lever 42. The lever 42, referring to FIG. 14, may be seen to be constituted as a roughly T-shaped element having a stem 44 and a cross bar 46. Provided inthe cross bar 46 are three spaced notches 48 which are engaged by the projections 40 on the coupler 32 so that when assembled the coupler is held in position between the bimetallic elements 26 and the lever 42 and is effective to transfer the downward motion of the bimetallic elements to the lever to cause the cross bar 46 and consequently the lever 42 to move downwardly. On the opposite end of .the stem 44 from the cross bar 46 the lever is provided with a pair of upstanding lugs 50, each having a notch 52 provided in its free end. The notches 52 engage apivot pin 54 held in a recess 56 molded into the lower body 6. The pivot pin is held in position by virtue of its engagement in the notches S2 of the lever which in turn is biased upwardly by a pair of coil springs 58 engaging between the back plate 8 and the bottom of the lever. Aholding plate 60 overlies the pin to hold it against upward movement while the holding plate itself is attached to a supporting surface 62 in the lower body 6 by a screw 64.

Extending to one side of the stem 44 is an arm 66 having a small notch 68 and a larger notch 70. Also provided in the arm 66 is a threaded opening 72. A clamp plate 74 provided with a semicircular depression 76 is attached to the arm 66 by means of a screw 78 engaging in the threaded opening 72. When attached to the arm 66, the clamp plate holds a pivot pin 80 in position between the arm and the depression 76. When assembled, the pivot pin 80 engages in holes in the ears 82 of an actuating lever 84. The actuating lever is formed with a pair of arms 86 carrying the ears 82 and a U-shaped portion 88 joining the arms 86. Coextensive with the arms 86 is an actuating arm 90. j

The actuating lever 84 may be formed of any suitable material preferably metallic'on one embodiment of the invention. In another embodiment thereof, the actuating lever 84 may be formed of a bimetallic material. When arm 90 is formed from a bimetallic material, a means is provided to compensate for variations in the ambient temperature, as the bimetallic construction of the element 26 is such that its free end tends to move downwardly as the temperature increases. If there should be a substantial increase in the ambient temperature, the device may operate or trip even though the desired thermal value is not reached by a heater 24. To prevent such nuisance tripping the actuating arm 90 may be formed of a bimetal arranged to cause it to move upwardly as the ambient temperature increases and thereby permit the actuator 92 to be moved upward by the force, of the coil spring 100. Under such a condition a greater downward movement of the actuating arm will be required to cause the device to trip.

Engaging the free end of the actuating arm 90 is an actuator 92. The actuator is formed with a completely enclosed opening 94 on its bottom and at its top it is formed with an opening 96 having an access slot 98. As may be best seen in FIG. 12, the free end of the actuator arm 90 engages in the opening 94 and the actuator 92 passes through an opening provided in the supporting surface 62 of the lower body 6. Engaging in the opening 96 of the actuator 92 is a coil spring 100 which passes through the opening 96 in such a way so that the actuator 92 engages the spring at approximately its center. The spring 100 has one end secured'to a contact assembly 102 asconstructed as follows. The contact assembly is formed with a basesection 104 having an opening 106 in the center thereof through which the actuator 92 passes when the device is assembled. Also provided on the contact assembly 102 are a pair of lugs 108 each formed with an upper portion 110 bent to form generally V-shaped elements. Extending upwardly from the rear of the base section 104 is a single bracket 112 provided with a hole therein which is used to anchor one end of the coil spring 100. A pair of spaced holes 114 are provided in the base section on either side of the bracket 112 to accommodate a pair of screws 116 which secure the contact assembly 102 to the supporting surface 62.

The contact assembly 102 supports a movable contact 118 formed generally as a U-shaped element with a pair of notches 120 in each leg thereof. The movable contact 118 is assembled to the contact assembly 102 by engaging the notches 120 in the generally V-shaped portions 110 of the upstanding lugs 108. The assembly is completed by connecting the other end of the coil spring 100 in a hole 122 provided in the cross leg of the movable contact 118. Provided on that same cross leg is a contact element 124. An electrical circuit for the movable contact 118 is completed by a terminal assembly 126 formed as a generally elongated bar having an upwardly bent portion 128 and an outwardly bent ,portion 130 at one end. A pair of threaded openings 132 are provided in the terminal assembly 126 to receive and hold the screws 116 after they have passed through the supporting surface 62 and, the holes 114 of the contact assembly 102 whereby the contact assembly and the terminal assembly 126 may be held in assembled position in the device, this being best seen in FIG. 13. The portion 130 of the terminal assembly extends through an opening provided in a side of the lower body 6 to provide an external means whereby an electrical connection may be made. i

In the normal or quiescent state, the movable contact 1 18 is held in anupward position using the engagement of the walls of the notches 120 with the V-shaped elements 110 of the lugs 108 as pivot points. The coil spring 100 is engaged in the opening 96 of the actuator 92 and inasmuch as this places the spring in tension the movable contact 118 is maintained in an uppermost position. The structure permitting this may be understood by reference to FIG. 12.

In that figure, it may be seen that the coil springs 58 exert an upward force on the bottom of the lever 42. Consequently, the actuating lever 84 which is attached thereto by virtue of the engagement of the pivot ,pin 80 with its arms 86 is maintained with its free end in an uppermost position and is held in that position by the vertical component of the spring force of the coil spring 100 acting through the actuator 92. In the event excess current should flow in the circuit being protected in any one of the conductors forming a part of that circuit, to the point that any one of the heaters '24 produces enough heat to cause its associated bimetallic actuator to deflect downwardly, the coupler 32 will transmit'the downward movement-of any such bimetallic actuator 26 to the free end of the lever 42. The lever will then pivot downwardly about the pin 54 causing the actuator lever 84 and its actuating arm to move downwardly pulling the actuator 92 likewise downwardly. The downward pulling force of the actuator is exerted at approximately the center of the coil spring secured at one end to the fixed bracket 112 and at its other end to the outer portion of the movable contact 118. When the downward force exerted by the actuator is sufficient to overcome the vertical force component of the coil spring the movable contact will pivot as described above with a snap or toggle action and in so doing will move from the solid line position shown in FIG. 12 to the'dotted line position of that figure.

Associated with the movable contact 118 is a relatively fixed contact 134 (see particularly FIGS. 6 and 15). The contact assembly 134 includes a terminal portion 136 and a spring contact portion 138. The spring contact portion is attached to the terminal portion 136 and the bottom 140 of the upper body 4 by means of a screw 142 holding these elements to that bottom. The

spring portion 138 carries a contact element 144 and is biased downwardly, that is, out of the plane of the drawing as shown in FIG. 6. At its free end there is provided a projection 146 for a purpose to be described. The terminal portion 136 extends outwardly of the housing to provide an exposed terminal 147 for connection to an actuating means in a circuit controller.

In one application of the invention, the actuating means may be the coil of a magnetic contactor which would normally be. energized through a circuit including one terminal connected to ground and the other connected to the terminal 147 through the terminal portion 136, spring contact portion 138, contact element 144, contact element 124, movable contact assembly 118, contact assembly 102 and the terminal assembly 126 to the terminal 130 and back to the terminal of a source of potential. As described above, in the event ofa thermal overload in the circuit being controlled by the contactor, the movable contact assembly 118 will operate so as to move the contact element 124 away from the contact element 144 interrupting the circuit to the magnetic contactor operating coil causing the contactor to drop out and interrupt the protected circuit so as to prevent any damage to the load being supplied;

As is best seen in FIGS. 7 and 15, an adjusting element 148 for determining operating value of the device is mounted in an opening 150 in a side wall 152 of the lower body 6. The adjusting element is constituted by a circular body having a hold 154 in the center thereof whereby it may be mounted on a pin or stud 156 molded on the lower body 6 and extending into the opening 150. Formed on the adjusting element 148 is a camming surface 158 extending partially around the periphery thereof. As is best seen in FIG. 5, also formed on the bottom of the actuating element 148 is an arcu- .ate projection 160 substantially coextensive with the camming element.

When assembled, the projection 146 of the contact assembly 134 bearsagainst the camming surface 158 so that as the actuating element 148 is rotated, the spring contact portion will move upwardly or downwardly as shown in FIG. 15. By rotating the adjusting element 148 the pressure or degree of engagement between the contact elements 144 and 124 may be varied and by this means the device adjusted by a user to vary its operating point. To increase the adjusting elements 148 resistance to rotation due to shock and vibration a wave washer 149 is placed on pin 156 and then the adjusting element 148 is assembled. The wave washer is compressed when the upper body 4 and lower body 6 is assembled and exerts additional pressure on the adjusting element 148. It should be noted that the slope of the camming surface 158 is such that if the adjusting element 148 should become loose the downward force exerted by the spring contact portion 138 will be effective to cause the element to rotate in the direction wherein less current in the circuit being protected will be required to cause the device to trip.

In order to provide a visual indication of the operating point the arcuate projection 160 is provided. Thus, when the adjusting element is assembled, the arcuate projection is disposed inside the lower body and one end or the other thereof will engage the interior of the sidewall 152 to. limit the movement of the adjusting element. For convenience and visual indication of the operating point, anotch 162 is provided in the adjusting element to receive the end of a pointed tool such as a screw driver whereby the desired adjustment may be made.

As described thus far, the apparatus may include means for compensating the variations in the ambient temperature and means for adjusting the operating value of the circuitprotector whereby to vary it to values equal to or greater than a nominal rated value. Infurther accordance with the invention, there is provided means for permitting an automatic reset or reclosure after a cessation of current flow in the circuit being protected and the heating element cools down' or in providing for a means requiring an operator tomanually reset the device. The basic elements permitting this are bestshown in FIGS. 11 and 15. These elements are constituted by an automatic reset spring 164. The contact spring assembly is formed as an elongated conducting member secured by threaded fastening means 166 to the supporting surface 62 in the lower body 6. It is, as may best be seen in FIG. 7, mounted substantially parallel to but spaced from the terminal assembly 126. Formed intermediate its length is a hump or raised portion 168 while its free end. 170 is bent, as is best shown in FIG. 15, first downwardly and .then laterally outwardly in thedirection of the outside of the housing 2.

The means whereby automatic or manual operation may be provided includes a reset cam 172v provided with a hold 174 in the center thereof, a raised camming surface 176 and an actuating projection 178. A wave washer 179 is provided to restrain movement of the reset cam 172. An opening 180 in the bottom of the side wall 152 of the lower body 6. is provided with a pin or stud 182 which may be inserted into the hole 174 of the reset cam 172 for mounting and permitting rotation of the same. When so mounted, the camming surface 176 is positioned within the lower body and is engaged by'the free end 170 of the automatic reset spring 164.

When it is desired to provide for automatic reset of the circuit protector, the actuating projection 178 of the reset cam 172 is engaged to rotate the reset cam to its maximum clockwise position as shown in FIG. 8. The limit of this position is determined by the engagement of'that projection with the side wall 152. When so rotated, a highermost point 184 of the camming surface 176 is in engagement with the free end 170 of the auto matic reset spring 164 causing the automatic reset spring to be bent upwardly about its point of attachment 166 with the supporting surface 62. When the automatic reset spring is so elevated and the apparatus operates in response to a thermal overload in the circuit, the movable'contact 118 will operate as previously described. However, the downward movement of its contact 124 will continue only until it engages the elevated automatic reset spring 164. Under these circumstances, the movable contact assembly will not be able to rotate far enough so as to assume an overcenter position, that is, a position wherein the force then being exerted by the coil spring 100 would be effective to maintain it in a downward position. Consequently, the movable contact 118 will only remain in its downward position in engagement with the elevated automatic reset spring 164 only as long as any one of the bimetal elements 26 is bending downwardly as the result of being heated by excess current flowing in one of the heater elements 24. As before, the contact 124 will have moved away from the contact 144 causing operation of a magnetic contractor of the like but with the interruption of the circuit as the result of the actuation of the contactor. The responsible heating element 24 will cool permitting the bimetal actuator 26 to restore itself to its original position. When this happens, the movable contact 118 will no longer be subjected to any force exerted by the actuator 92 and the coil spring will be effective to cause the movable contact assembly to rotate upwardly as shown in FIG. 12 and the contact 124 will reengage the contact 1 44causing the magnetic contactor to operate and restore the circuit.

When it is desired to provide for manual operation of the apparatus, the actuating projection 178 of the reset cam 172 is rotated to its maximum counterclockwise (as viewed from FIG. 8) position as shown in FIG. 8 and this in turn will bring the free end of the automatic-reset spring 164 into engagement with the lowermost portion 186 of the cam 176. Under these circumstances, the automatic reset spring 164 is permitted to be lowered close to the supporting surface 62 and when the device operates the movable contact 118 is permitted to rotate to the dotted line position shown in FIG. 12wherein the coil spring 100 is now effectiveto exert a force tending to maintain it in that position.

When the device is so adjusted, it is necessary to use the manual reset means provided. This means cornprises a manual reset actuator 188 formed as a plungerlike element out of a non-conducting material such as a suitable plastic. The upper end of the reset actuator is mounted vertically in the apparatus extending through an opening molded in divider 16 (see FIG. 13). The reset actuator 188 is maintained in an upward position by a coil spring 190 engaging between a recess 192 in I tuating arm 196 engages the leg of the U-shaped movable contact 118 to exert a force thereon causing it to move in a counterclockwise direction. Therefore, when the apparatus has operated in response to a thermal overloadin the circuit and the movable contact 118 has moved downwardly or rotated clockwise as shown in FIG. 12, when the reset actuator is operated, the actuating arm 196 is effective to cause the movable contact assembly to move upwardly or rotate in a counterclockwise direction and to reestablish engagement of the contact 124 with the contact 144.

In addition to the foregoing features, the apparatus also includes a manual means whereby a user may periodically check the Operation of the device. This means is provided by a manual trip plunger 198. The manual trip plunger 198 isformed as a substantially cylindrical element passing through an opening provided in a divider 16 (see FIG. 1). Referring to FIG. 12, it may be seen that the manual trip plunger includes an upper enlarged portion 200 and a reduced lower portion 202. The opening in the divider 16 is molded to have a lower portion 204 of a first diameter and an upper portion 206 of a second and greater diameter. Encompassing the manual reset plunger is a coil spring 208 extending between the bottom of the portion 206 of the opening in the divider l6 and the bottom of the upper enlarged portion 200 so as to exert a force biasing the trip plunger upwardly. A collar 210 is passed over the reduced portion 204 of the trip plunger 198 encompassing the bottom of the reduced portion and bearing against the bottom 212 of the upper body 4 so as to maintain the trip plunger in assembled position in the device. The bottom 214 of the trip plunger is positioned to overlie the forward or contact end of-the movable contact 118 so that when the trip plunger is moved downwardly against the force of the spring 208 the movable contact assembly will be rotated downwardly or clockwise interrupting the circuit between the contacts 124 and 144. By this means an operator can test the apparatus and the circuit controlling element controlled thereby periodically as desired.

The apparatus as described thus far-is one in a normally closed configuration, that is, the contact 124 is normally engaged with the contact 144 so as to normally energize a holding element in the circuit to be protected. In an alternative embodiment, the device could be constructed in a transfer contact configura- I tion. Thus, in this embodiment the automatic reset spring 164 may be provided with a contact element and a terminal such as shown at 216 in FIG. 3 extending outwardly of the housing. In this arrangement, the movable contact assembly 118 with an additional contact on it would, during the normal or quiescent state, he maintained in its upward position as shown in FIG. 12 and upon actuation in response to excess current flow in the circuit being protected would be actuated to engage the contact on the automatic reset spring'164 to close a circuit effective to energize a circuit controlling device.

This same arrangement, that is, the provision of a contact element on the automatic reset spring 164 together with an external terminal 216 may also be 4 other kind of indicator to advise a user that the device has tripped and that there is or was a thermal overload in the circuit.

Also included in the device are convenient means which may be utilized during the manufacture of the device to make adjustments whereby the effect of tolerances in the various components thereof, such as the thermal coefficients of expansion of the bimetals or dimensional tolerances in the parts, may be substantially eliminated. v

FIG. 12 illustrates one such adjusting means. This in-' cludes a member 218 threaded into a boss 220 molded on the upper surface of the back plate 8 and engaging U-shaped portion 88 of the actuating lever 84. The

threaded element 218 may be utilized after the device has been assembled and connected in a test circuit with known values and moved inwardly or outwardly to cause the actuating lever 84 to pivot about the pin until a setting is found at which the device will operate at its rated value. In this manner, any tolerances in the materials may be compensated for by adjusting the device once assembled to a precise operating value.

Another adjusting means is provided by the screw 64 which by engaging in the holding plate 60 maintains the holding plate in position so that it bears on the pivot pin 54 about which the lever 42 pivots. Access to this screw is provided through an opening 222 in the back plate 8 whereby the balance adjustment of the lever may be achieved.

In addition to the foregoing features, the device also includes an additional adjustment and safety feature. This is provided by a threaded element 224 to which access may be had by an opening 226 in the bottom of the back plate and aligned with an opening 228 in the lever 42. The upper end of this threaded element engages a bottom surface of the reset plunger 188 to limit its downward movement. In this fashion, if the device has tripped and a user manually resets the device so as to reclose the circuit but the condition causing the thermal overload still exists causing any one of the bimetal actuators to be deflected downwardly that bimetal actuator will still be effective to maintain the movable contact assembly 118 in its downward position interrupting the circuit. In this fashion, an operator cannot reset a circuit wherein a fault or other condition causing a thermal overload still exists.

Another safety feature to be used at the option of a user includes a slot 229 formed in the bottom of the reset cam 172 (see FIG. 8). This slot cooperates with a slot 230 formed in the bottom of the lower body 6. When the reset cam 172 is rotated counterclockwise to the manual reset position, the slots 229 and 230 are aligned with each other and a metal strip can be inserted to engage in these slots so as to prevent rotation of the reset cam away from the manual reset position. Such anarrangement would require in the event of the device tripping out that an operator manually reset it and at the same time he would investigate and ascertain the reason why the device operated. Similarly slots (not shown) are provided on the adjusting element 148 and the top of the side wall 152 to permit the insertion of a holding element in those slots to prevent rotation of the adjusting element if such is not desired.

Beyond those modifications and variations which have been described above, there are others which may occur to those skilled in the art and it is intended by the claims appended hereto to cover all such modifications as fall within their scope.

What is claimed as new and desired to be secured by Letters Patent is:

1. An improved electrical circuit protection device comprising: a housing; a plurality of pairs of terminals mounted on said housing for connection in an electrical circuit to be protected; an electrical heating element extending between each terminal in a pair of terminals; a bimetallic strip, anchored at one end was to have flexing movement toward the interior of said housing at its opposite free end in response to increased temperature, mounted on said housing beneath each heating element; a pivoted lever assembly mounted in said housing spaced from said' terminals; a coupler having a plurality of first extensions, each'engaging a free end of i one of said bimetallic strips; said coupler also having a plurality of second extensions extending oppositely from said first extensions and engaging the free end of said pivoted lever assembly to cause it to move in response to movement of any one of said bimetallic strips; an actuating lever pivotally mounted on said lever assembly and substantially coextensive therewith;

a switch supporting bracket mounted in said housing contact; a second terminal disposed externally of said housing; a first relatively fixed contact in said housing; and means electrically connecting said second terminal to said first relatively fixed contact.

2. An improved electrical circuit protection device as set forth in claim 1 including an adjustable element mounted beneath said movable contact assembly to limit its downward movement.

3. An improved electrical circuit protection device as set forth in claim 2 wherein said, adjustable means comprises an elongated spring member fixed at one end and free to move at its, other end and an intermediate portion thereof is positioned in the path of movement of said movable contact so that when said elongated spring member is moved to one position it will be engaged by and limit the movement of said movable contact as it is operated and when moved to another position it will permit greater movement of said movable contact and said coil spring will tend to urge said movable contact in another direction.

4. An improved electrical circuit protection device as set forth in claim 3 having a rotatable element with a portion extending externally of said housing and engaging the free end of said elongated spring member whereby it may be adjusted.

5. An improved electrical circuit protection device as set forth in claim 4 including a third terminal on the exterior of said housing, a second relatively fixed contact on said adjustable element and means electrically connecting said third terminal to said second relatively fixed contact.

6. An improved electrical circuit protection device as set forth in claim 4 wherein said rotatable element includes a cam portion and one end of said elongated spring member engages said cam portion.

7. An improved electrical circuit protection 'device as set forth in claim6 including means formed on said housing and in said rotatable element for receiving means to prevent the rotation of said rotatable element.

8. An improved electrical circuit protection device as set forth in claim 1 wherein said movable contact is normally urged by said coil spring toward engagement with said first relatively fixed contact and upon movement of said coupler lever assembly, actuating lever and actuator in response to the movement of any one of said bimetal strips caused by the heat developed in an associated heating element as the result of excess current flow in a circuit being protected said movable contact will move away from said relatively fixed contact.

9. An improved electrical protection device asset forth in claim 8 wherein said means connecting said second terminal to said first relatively fixed contact includes a leaf spring secured at one end free to move at its other end.

10. An improved electrical circuit protection device as set forth in claim 9 including a rotatable adjusting element having a portion extending externally of said housing and having a portion engaging the free end of said leaf spring whereby the leaf spring may be moved upward or downwardly in response to movement of said adjusting element.

11. An improved electrical circuit protection device as setforth in claim 10 wherein said adjusting element is provided with a cam surface interiorly of said housin g and the free end of said leaf spring is in contact with said cam surface.

12. An improved electrical circuit protection device as set forth in claim 1 including a reset actuator mounted in said housing and having a portion disposed exteriorly thereof, spring means engaging said reset actuator to urge it outwardly of said housing and means on said reset actuator overlying a portion of said movable contact whereby when said reset actuator is moved inwardly against the force of the spring and said movable contact assembly is in one position the movement of said manual reset actuator will be effective to cause it to move to another position.

13. An improved electrical circuit protection device as set forth in claim 12 including adjustable means positioned beneath said manual reset actuator to limit its movement inwardly of said housing.

' 14. An improved electrical circuit protection device as set forth in claim 13 wherein said housing is provided with an opening therein to provide access to said adjustable means whereby it may be adjusted.

15. An improved electrical circuit protection device,

as set forth in claim 1 including a manual trip plunger having a portion extending externally of said housing, spring means engaging said manual trip plunger to urge it outwardly of said housing, said manual trip plunger being disposed above said movable contact whereby when said manual trip plunger is depressed inwardly of said housing against the force of said spring it will engage said movable contact assembly and cause it to move from a first position to a second position.

16. An improved electrical circuit protection device as set forth in claim 1 wherein said actuating lever is formed of a bimetallic material arranged so that its free end moves in a direction opposite to the direction of movement of said bimetallic strips so as to provide compensation for variations in the ambienttemperature.

17. An improved electrical circuit protection device as set forth in claim 16 including an adjusting screw threaded into said housing and having an end engaging said actuating lever to permit adjustment of the device to a desired operating value and wherein an opening is provided in said housing for access to said adjusting screw.

18. An improved electrical circuit protection device asset forth in claim 4 wherein said movable contact is normally urged by said coil spring toward engagement with said first relatively fixed contact and upon movement of said coupler lever assembly, actuating lever and actuator in response to the movement of any one of said bimetal strips caused by the heat developed in an associated heating element as the result of excess current flow in a circuit being protected said movable contact will move away from said relatively fixed contact.

19. An improved electrical circuit protection device as set forth in claim 19 wherein said means connecting said second terminal to said first relatively fixed contact includes a leaf spring secured to one end free to move at its outer end.

20. An improved electrical circuit protection device as set forth in claim 19 including a rotatable adjusting element having a portion extending externally of said housing and having a portion engaging the free end of said leaf spring whereby the leaf spring may be moved upward or downwardly in response to movement of said adjusting element.

21. An improved electrical circuit protection device as set forth in claim 20 wherein said adjusting element is provided with a cam surface interiorly of said housing and the free end of said leaf spring is in contact with said cam surface.

22. An improved electrical circuit protection device as set forth in claim 21 including a reset actuator mounted in said housing and having a portion disposed exteriorly thereof, spring means engaging said reset actuator to urge it outwardly of said housing and means on said reset actuator overlying a portion of said movable contact whereby when said reset actuator is moved inwardly against the force of the spring and said movable contact assembly is in one position the movement of said manual reset actuator will be effective to cause it to move to another position.

23. An improved electrical circuit protection device as set forth in claim 22 including a manual trip plunger having a portion extending externally of said housing,

spring means engaging said manual trip plunger to urge it outwardly of said housing, said manual trip plunger being disposed above said movable contact whereby when said manual trip plunger is depressed inwardly of said housing against the force of said spring it will engage said movable contact assembly and cause it to move from a first position to a second position.

24. An improved electrical circuit protection device as set forth in claim 23 including a third terminal on the exterior of said housing, a second relatively fixed contact on said adjustable element and means electrically connecting said third terminal to said second relatively fixed contact.

25. An improved electrical circuit protection device as set forth in claim 24 wherein said actuating lever is formed of a bimetallic material arranged so that its free end moves in a direction opposite to the direction of movement of said bimetallic strips so as to provide compensation for variations in the ambient temperature. 

1. An improved electrical circuit protection device comprising: a housing; a plurality of pairs of terminals mounted on said housing for connection in an electrical circuit to be protected; an electrical heating element extending between each terminal in a pair of terminals; a bimetallic strip, anchored at one end so as to have flexing movement toward the interior of said housing at its opposite free end in response to increased temperature, mounted on said housing beneath each heating element; a pivoted lever assembly mounted in said housing spaced from said terminals; a coupler having a plurality of first extensions, each engaging a free end of one of said bimetallic strips; said coupler also having a plurality of second extensions extending oppositely from said first extensions and engaging the free end of said pivoted lever assembly to cause it to move in response to movement of any one of said bimetallic strips; an actuating lever pivotally mounted on said lever assembly and substantially coextensive therewith; a switch supporting bracket mounted in said housing between said bimetallic strips and said lever assembly; a movable contact mounted on said switch supporting bracket; a coil spring extending between said switch supporting bracket and said movable contact tending to urge said movable contact in one direction; an actuator engaging said spring and said actuating lever to exert a force on said spring when said actuating lever moves downwardly in response to downward movement of said pivoted lever assembly; a first terminal disposed externally of said housing and means electrically connecting said first terminal to said movable contact; a second terminal disposed externally of said housing; a first relatively fixed contact in said housing; and means electrically connecting said second terminal to said first relatively fixed contact.
 2. An improved eLectrical circuit protection device as set forth in claim 1 including an adjustable element mounted beneath said movable contact assembly to limit its downward movement.
 3. An improved electrical circuit protection device as set forth in claim 2 wherein said adjustable means comprises an elongated spring member fixed at one end and free to move at its other end and an intermediate portion thereof is positioned in the path of movement of said movable contact so that when said elongated spring member is moved to one position it will be engaged by and limit the movement of said movable contact as it is operated and when moved to another position it will permit greater movement of said movable contact and said coil spring will tend to urge said movable contact in another direction.
 4. An improved electrical circuit protection device as set forth in claim 3 having a rotatable element with a portion extending externally of said housing and engaging the free end of said elongated spring member whereby it may be adjusted.
 5. An improved electrical circuit protection device as set forth in claim 4 including a third terminal on the exterior of said housing, a second relatively fixed contact on said adjustable element and means electrically connecting said third terminal to said second relatively fixed contact.
 6. An improved electrical circuit protection device as set forth in claim 4 wherein said rotatable element includes a cam portion and one end of said elongated spring member engages said cam portion.
 7. An improved electrical circuit protection device as set forth in claim 6 including means formed on said housing and in said rotatable element for receiving means to prevent the rotation of said rotatable element.
 8. An improved electrical circuit protection device as set forth in claim 1 wherein said movable contact is normally urged by said coil spring toward engagement with said first relatively fixed contact and upon movement of said coupler lever assembly, actuating lever and actuator in response to the movement of any one of said bimetal strips caused by the heat developed in an associated heating element as the result of excess current flow in a circuit being protected said movable contact will move away from said relatively fixed contact.
 9. An improved electrical protection device as set forth in claim 8 wherein said means connecting said second terminal to said first relatively fixed contact includes a leaf spring secured at one end free to move at its other end.
 10. An improved electrical circuit protection device as set forth in claim 9 including a rotatable adjusting element having a portion extending externally of said housing and having a portion engaging the free end of said leaf spring whereby the leaf spring may be moved upward or downwardly in response to movement of said adjusting element.
 11. An improved electrical circuit protection device as set forth in claim 10 wherein said adjusting element is provided with a cam surface interiorly of said housing and the free end of said leaf spring is in contact with said cam surface.
 12. An improved electrical circuit protection device as set forth in claim 1 including a reset actuator mounted in said housing and having a portion disposed exteriorly thereof, spring means engaging said reset actuator to urge it outwardly of said housing and means on said reset actuator overlying a portion of said movable contact whereby when said reset actuator is moved inwardly against the force of the spring and said movable contact assembly is in one position the movement of said manual reset actuator will be effective to cause it to move to another position.
 13. An improved electrical circuit protection device as set forth in claim 12 including adjustable means positioned beneath said manual reset actuator to limit its movement inwardly of said housing.
 14. An improved electrical circuit protection device as set forth in claim 13 wherein said housing is provided with an opening therein to provide Access to said adjustable means whereby it may be adjusted.
 15. An improved electrical circuit protection device as set forth in claim 1 including a manual trip plunger having a portion extending externally of said housing, spring means engaging said manual trip plunger to urge it outwardly of said housing, said manual trip plunger being disposed above said movable contact whereby when said manual trip plunger is depressed inwardly of said housing against the force of said spring it will engage said movable contact assembly and cause it to move from a first position to a second position.
 16. An improved electrical circuit protection device as set forth in claim 1 wherein said actuating lever is formed of a bimetallic material arranged so that its free end moves in a direction opposite to the direction of movement of said bimetallic strips so as to provide compensation for variations in the ambient temperature.
 17. An improved electrical circuit protection device as set forth in claim 16 including an adjusting screw threaded into said housing and having an end engaging said actuating lever to permit adjustment of the device to a desired operating value and wherein an opening is provided in said housing for access to said adjusting screw.
 18. An improved electrical circuit protection device as set forth in claim 4 wherein said movable contact is normally urged by said coil spring toward engagement with said first relatively fixed contact and upon movement of said coupler lever assembly, actuating lever and actuator in response to the movement of any one of said bimetal strips caused by the heat developed in an associated heating element as the result of excess current flow in a circuit being protected said movable contact will move away from said relatively fixed contact.
 19. An improved electrical circuit protection device as set forth in claim 19 wherein said means connecting said second terminal to said first relatively fixed contact includes a leaf spring secured to one end free to move at its outer end.
 20. An improved electrical circuit protection device as set forth in claim 19 including a rotatable adjusting element having a portion extending externally of said housing and having a portion engaging the free end of said leaf spring whereby the leaf spring may be moved upward or downwardly in response to movement of said adjusting element.
 21. An improved electrical circuit protection device as set forth in claim 20 wherein said adjusting element is provided with a cam surface interiorly of said housing and the free end of said leaf spring is in contact with said cam surface.
 22. An improved electrical circuit protection device as set forth in claim 21 including a reset actuator mounted in said housing and having a portion disposed exteriorly thereof, spring means engaging said reset actuator to urge it outwardly of said housing and means on said reset actuator overlying a portion of said movable contact whereby when said reset actuator is moved inwardly against the force of the spring and said movable contact assembly is in one position the movement of said manual reset actuator will be effective to cause it to move to another position.
 23. An improved electrical circuit protection device as set forth in claim 22 including a manual trip plunger having a portion extending externally of said housing, spring means engaging said manual trip plunger to urge it outwardly of said housing, said manual trip plunger being disposed above said movable contact whereby when said manual trip plunger is depressed inwardly of said housing against the force of said spring it will engage said movable contact assembly and cause it to move from a first position to a second position.
 24. An improved electrical circuit protection device as set forth in claim 23 including a third terminal on the exterior of said housing, a second relatively fixed contact on said adjustable element and means electrically connecting said third terminal to said second relatively fixed contaCt.
 25. An improved electrical circuit protection device as set forth in claim 24 wherein said actuating lever is formed of a bimetallic material arranged so that its free end moves in a direction opposite to the direction of movement of said bimetallic strips so as to provide compensation for variations in the ambient temperature. 